A current rise in environmental awareness leads to preparation of a legal framework for preventing fuel volatilization. In particular, the field of automobiles, mainly in the United States, shows a significant tendency of suppressing fuel volatilization, and has an increasing need for materials having excellent fuel barrier properties.
Specifically, a laminated hose including a fluororesin barrier layer (layers other than the barrier layer are rubber layers) for achieving favorably low fuel permeability is used as a fuel-transporting rubber hose. Still, a strong demand for reduction in environmental load causes a requirement for much lower fuel permeability.
Fluororubber is excellent in various properties such as heat resistance, oil resistance, and aging resistance, and thus is proposed to be used as a rubber material for the layers other than the above barrier layer.
However, the fluororesin, when used for the barrier layer, has difficulty in bonding to the fluororubber, the counter material, of the inner and outer layers. In the case of using the fluororubber for the inner and outer layers, traditional techniques have only achieved relatively easy bonding between a fluororesin having poor fuel permeability and a fluororubber.
For example, Patent Literature 1 discloses a hose for fuel pipes of automobiles, including a firmly bonded laminate of an inner layer that is a molded article of a tetrafluoroethylene/hexafluoropropylene/vinylidene fluoride ternary fluororesin, an outer layer that is a cross-linked molded article of an epichlorohydrin rubber blended with a 1.8-diazabicyclo(5.4.0)undecene-7 salt and an organic phosphonium salt or a blend of NBR/PVC, and an innermost layer that is a cross-linked molded article of a composition for cross-linking of NBR rubber or fluororubber blended with a 1.8-diazabicyclo(5.4.0)undecene-7 salt and an organic phosphonium salt.